Explosive



W O C S C A EXPLOSIVE Filed March 17, 1933 INVENTOR IEWLQSWE Alexander ilruiclk. sate, raven Application March 1'3, 1983, Serial No. 661,323 in Great Britain. February 24, 1932 This invention. comprises improvements in or relating to explosives.

It is an object of the present invention to provide an explosive charge capable of safe use in fiery mines and in like places which is characterized not by detonation but by the application of gaseous pressure in the bore hole in which it is exploded so that mineral, for example coal, which is being blasted by the explosive, may be recovered safely and in large pieces.

According to the present invention, .an explosive charge consists of a container in which is placed a quantity of a salt which is decomposable by heat so as to yield non-inflammable gaseous products of decomposition together with a heating element consisting of a self-combustible mixture, and means to ignite the same.

One salt which is conveniently used, according to the present invention, is ammonium nitrate. Hitherto, ammonium nitrate has been known to be capable of detonation by means of very powerful detonators, but it will'be understood that detonation is not aimed at inthe present invention, and ammonium nitrate is merely decomposed in a cylinder which is designed with a safety-disc closure at one end, relatively easily rupturable by the internal pressure generated, so as to allow of the sudden escape of the gaseous products of decomposition. The eflfect is the production of a pressure of innocuous gases within the cylinder, sufiicient to burst the safety disc and to give the effect of an explosion. However, as will be observed, the cylinder is not, in normal storage before use, subject to any internal pressure.

A preferred form of heating element is one consisting of a mixture of an oxygen-carrying salt, for example, potassium chlorate or perchlorate with a fuel.

If desired, the nature of the explosion may be modified by the inclusion of other salts along with the principal decomposable salt which is used. For example, chlorides such as ammonium chloride may be mixed with ammonium nitrate.

The accompanying drawing illustrates dia grammatically a type of container suitable for use in connection with the explosive charge which forms the subject of the present invention. Containers of this general type are already in use for holding compressed carbon dioxide charges.

In the drawing 11 represents the body oi: the container which has a seating 12 near one end on which rests a shearable' steel disc 13 held in place by a screwed plug 14. The plug has an internal passage 15 communicating with four outlet orifices 16 drilled transversely in the end 01 the plug. Thus, when the heating charge is decomposed and internal pressure generated in the container suilicient to shear the disc 13, the

sheared ofi portion of the disc is forced through 0 the passage 15 past the opening 16 in the end of the passage and the gases under pressure rush out through the transverse openings 16.

The sheared portion of the disc can subsequently be removed from the screwed plug 14 by or a drift driven in through an aperture 17 in the end of the plug.

Within the container 11 is a heating charge 18 which contains an electrically-fired igniting charge or detonator 19. The igniting charge is 763 connected by twin electrical wires 20 to a source of electricity and the wires 20 pass through a plug 21 screwed in the other end of the container through the plug 14.. A gland nut 22 is provided and serious leakage through the gland nut is obw viated by a readily compressible washer 23 which grips the twin electric wires.

It will be understood that the pressure at which the gases are released is dependent upon the strength of the shearable steel disc 13, which is chosen according to the pressure desired. After use the container is cleaned out and fitted with a new charge and disc and can therefore be used again. It will be observed that the arrangements may be somewhat simpler thanwhen such a container is employed charged with carbon dioxide because there is no need to guard against leakage in storage of gas under pressure.

The following tests were'carried out in steel containers such as 11 having an internal diam- W eter of about 1%," and 30" in length. The container had a heater charge 18 consisting of a cellulose acetate and potassium perchlorate mixture and the thickness of the shearing disc 13 on the end of the steel container was 7/64", while its shearing diameter was three-quarters of an inch. The heating charge was electrically ignited in the usual way.

. Test 1 TestZ- The heating mixture was reduced to 50 grams in amount, the amount of ammonium nitrate being maintained at 130 grams. The disc wasduly sheared, but only after a delay of 4 seconds, indieating that the amount of the heating mirture was barely suficient.

Test 3 in place of ammonium nitrate the cylinder was charged with ammonium chloride, 200 grams, and

heater containing 64 grams of heating mixture.-

The result was an explosion, but there was an undecomposed residue or" ammonium chloride amounting to 119 grams.

Test a The cylinder was charged with 260 grams of a mixture. of ammonium chloride 25% and ammonium nitrate 25%. The heater contained 65 grams of mixture. 7 The result was a violent explosion without any undecomposed residue.

Test 5 Using a larger proportion of aonium chloride compared with ammonium nitrate (50% of each), and a somewhat smaller quantity (130 grams) with a heating charge of 50 grams, it was found that no sufiicient pressure was produced to shear the disc at the end of the cylinder.

Another salt which can be employed insteadof sodium chloride with the object of absorbing heat and g the violence of the explosion is ammonium oxalate. In the following test a mixture was used of 84% ammonium nitrate and 16% onium gxalate. 200 grams of this was employed as the charge and 50 grams of heater. In a test made in hard sandy ground the shot broke up the ground well.

Test 8 In this case 175 grams of straight ammonium nitrate was employed and the heating charge was reduced to grams; The heating charge was packed in close contact with the ammonium nitrate charge in the container and the result was an excellent shot, no residue being left in the shell and no delay in the explosion being noticed.

Test 9 In this case a similar mixture to that employed in Test 6 was used but 250 grams of ammonium nitrate was employed instead of 150 grams and the heating charge consisted of grams only. The result was an excellent shot.

. Test 1' In this test a smaller shell was used for the charge having an internal volume of 300 cubic centimeters. 87 grams of straight ammonium nitrate was used in conjunction with 20 grams of heating charge; this again gave excellent results.

Test 11 wide limits. with as much as 40% of sodium chloride.

tate and asbestos, inthe present case ordinary black powder was employed to an amount of 30 grams. The result was an excellent shot.

The following general remarks convey additional data:--When cooling salts are employed the percentage of these salts may vary within Good results have been obtained Other salts which can be used satisfactorily are ammonium oxalate as specified in the above tests and sodium bicarbonate, zinc sulphate, magnesium sulphate, sodium sulphate and the lilre. These salts absorb heat in the course of decom= position and serve to minimize the violence of the explosion while yielding non-inflammable gase= ous products.

It is preferable that the ammonium nitrate employed should be granular in form, say such as would pass through a screen having 8 meshes to the lineal inch and will not pass a screen which has meshes to the lineal inch. It is sometimes desirable to admix the ammonium nitrate with, say, 1% to 2% asbestos fibre with the object ct preventing binding and recrystallization with the material after it has been charged into the shell.

The quantity of heating compcsiton employed should preferably be adequate to afiord heat nec= essary for the reaction of the decomposable salt which, when ammonium nitrate is employed is as follows:

'2NH4NO3=2N2+4H2O+O2 I claim:

1. An explosive charge comprising in combination a container in which is placed a quantity of a salt decomposable by heat so as to yield noninfiammable gaseous products of decomposition, together with a heating element consisting of a mixture of potassium perchlorate and cellulose acetate and means to ignite the same.

2. An explosive charge consisting of a container capable of withstanding a high internal pressure and having an aperture closed by a relatively easily rupturable disc, said container being charged with a quantity of a salt decomposable by heat so as to yield non-inflammable gaseous products of decomposition together with a potassium-chlorine salt and a fuel and means to ignite the same.

3. An explosive charge consisting of a container capable of withstanding a high internal pressure and having an aperture closed by a relatively easily rupturable disc, said container being charged with a quantity of a salt decomposable by heat so as to yield non-inflammable gaseous products of decomposition together with potassium chlorate and a fuel and means to ignite the same.

4. An explosive charge comprising in combina= tion a container adapted to withstand-a high internal pressure, a relatively easiiy shearable disc closure therefor, a charge comprising ammonium nitrate within the container a heating element consistingof a cartridge oi-potassiurnv perchlo rate and a fuel and means to ignite the heating element.

5. An explosiyecha'rge consisting oi a container capable of withstanding a high internal pressure and having an aperture closed by a relatively easily rupturable disc, said container being charged with a quantity of an ammonium salt decomposable by heat, with which is ad- -mixed a second salt less readily decomposable by heat, together with a heating element consisting lit? Lemmas 7. An explosive charge comprising in combination a container in which is placed a quantity of a salt decomposable by heat so as to yield non-inflammable gaseous products of decomposition, which salt is admixed with a second salt less readily decomposable by heat, together with a heating element consisting of a mixture of potassium perchlorate and cellulose acetate and means to ignite the same.

ALEXANDER CRUICKSHANK SCOTT. 

